1. Field of the Invention
The present invention relates to a reel winding device for a material web reel that includes a reel lightening device with a blow box coupled to a compressed air supply, and to a process for lightening a material web reel in a winding and/or unwinding device. Further, the features of the present invention may be utilized both during winding and unwinding of material web reels. In both cases, similar problems may be solved in a same manner.
2. Discussion of Background Information
In order to reduce setup times, those who work with paper web reels, e.g., printing plants, want increasingly larger paper web reels, i.e., a larger paper web supply. Currently, the trend in the industry is to produce web reels having widths of more than 3 meters and reel diameters of more than 1.5 meters.
However, as the web reel widths become relatively large, the increased weight of the reel, when a certain reel diameter is exceeded, results in sagging of the paper web reel. In this case, the core, which is usually designed as a pasteboard tube, is no longer capable of providing the necessary rigidity.
This sagging during winding has been countered in the prior art by supporting the paper reel from beneath. However, this arrangement requires that the paper reel rest with a certain bearing force on the support, and the bearing pressure determines reel hardness. Thus, because the weight of the reel increases during winding, there is a danger that the reel hardness will increase from the inside out, which is an undesirable hardness pattern.
To avoid affecting reel hardness in this manner, the prior art has proposed to support the reel via an air cushion. In this case, the reel weight is distributed over a relatively large surface such that the bearing pressure remains low.
A blow box, which is fed compressed air from a compressed air supply, is used to generate the air cushion. The blow box is pivoted toward the paper reel as soon as the reel diameter exceeds a specific value of, e.g., approximately 500 mm. To prevent damage to the paper reel, a gap must be maintained between the reel and the blow box. However, this also results in significant energy losses due to escaping compressed air. Further, the pressure relationships in the blow box and, thus, the extent of lightening are permanently altered, particularly since the weight of the paper reel is subject to change as a result of the winding or unwinding.